AU650338B2 - A method for the manufacture of a priming material - Google Patents

Abstract

The use of a mixture which contains a matrix-forming glass powder and, as opacifying agent, 10 to 60 % by weight of ZrO2 with average particle sizes between 0.1 mu m and 5 mu m for the preparation of a primer for coating a metallic dental crown or bridge by moistening with a liquid.

Description

1 6503358

AUSTRALIA

Patents Act 1990 IVOCLAR AG

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: A METHOD FOR THE MANUFACTURE OF A PRIMING MATERIAL The following statement is a full description of this invent-ion including the best method of performing it known to us:- L 1 i -1A- The invention relates to a method for the manufacture of a priming material for the overlaying or coating of a metallic tooth crown oor bridge by using a mixture which contains a matrix-forming glass powder and an opacifier.

When manufacturing metal tooth crowns and bridges which are faced with plastics or ceramic material, it is necessary to overlay the metal framework with a priming material a socalled opaquer in order that the dark metallic ground is covered and the metal l-O does not gleam through. Without such an opaquer the colour of the finished facing, which is to match the colour of the remainder of the denture as closely as possible, cannot be exactly eproduced.

2C? Known from DE-PS 33 32 179 are priming materials for dental purposes based on polymerizable methacrylic acid esters which contain a mixture of titanium dioxide and zirconium dioxide as pigment, in which a considerable titanium dioxide content, namely of up to 50 is provided. The priming materials of the examples contain 25 titanium dioxide. They are used to ccver metal frameworks for crowns with plastics facings.

The prior art cited in column 2 of this published document, namely Kirk-Othmer, Encyclopedia of Chemical Technology, 2nd edition, New York (1970), Volume 22, 651-653, reveals that the use of zirconium dioxide as ceramic opacifier and as pigment or opacifier for ceramic glazes and enamels was known. There is no suggestion however that zirconium dioxide be used as an additive for a metal ceramic opaquer, i.e. for a ceramic, in particular glass ceramic priming material for the overlaying of metal crowns or bridges, where it must be borne in mind that such an opaquer

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2 must satisfy special requirements. For example, such an opaquer must be deposited on a crown in thin layers of at most 0.5 mm and then be capable of being stoved, the crown to be completely covered by the brightly gleaming opaquer layer after stoving.

DE-PS 37 43 609 describes a light-permeable glass ceramic which comprises fine crystals of calcium phosphate which are uniformly dispersed in a glass matrix based on Si02-A02-ZrO2. It is important as bio-material and has advantageous thermal, electrical and mechanical properties. The glass ceramic is transparent or semi--transparent. Zirconium dioxide is added as nucleation or germination agent. The glass ceramic can be used as adhesive or binder for ceramic mass materials or metals.

There is no reference in this publication to the use of a zirconium dioxide-containing glass ceramic as opaquer for the dental sector. Essential, quite to the contrary, is the light permeability of the glass ceramic, for which reason this publication states precisely the opposite of what one skilled in the art expects from an opaquer.

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EP-PS 119 062 discloses pasty materials made from porcelain powder and water with added ceramic particles of a particle size below 0.3 um. The materials can be used as opaquer for crowns with porcelain facings.

Known from DE-OS 3 902 771 is a stovable silicatic material for the manufacture of dentures which serves as connection material and for the masking of the metallic colour alloy surface. The object to be achieved should be to provide a silicatic material which consists of a readily flowing base melt and a proportion of opaquer, the composition and expansion coefficient of which are set in such a way that it is stovable onto a dental prosthesis section which can be manufactured from noble metal alloys of the silver/palladium type or from dental non-metal alloys of the base types nickel/ chromium and cobalt/chromiun; 1 3 and forms a gap-free connection to a dental plastics material after its silanization. The silicatic material proposed here is distinguished by a high titanium dioxide content (15.0 16.5 and relatively small zirconium dioxide contents (4 to The disadvantages of the opaquers of DE-PS 33 32 179, EP-PS 119 062 and DE-OS 39 02 771 are lack of covering power and adhesion.

In the crown edges sector in particular, the stoving of the known opaquers is followed by unwanted discolorations which seriously impair the cosmetics of the succeeding facings. This is also true of the opaquers known to one skilled in the art which have been commercially available for some time.

The object of the invention is to make available a method for the manufacture of a priming material for dental purposes, namely for the overlaying or coating of dental metal frameworks prior to facing and also a priming material in particular for ceramics facings with improved covering power and adhesion, the adhesion of which both to metal and to the facing ceramic is excellent, which can be easily applied and stoved and which, particularly in the area of the crown edges, reliably covers the metal. The discolorations occurring above all with NE alloys (non-noble metal alloys) are also to be avoided after the stoving.

It was now surprisingly discovered that by adding larger quantities of zirconium dioxide as opacifier to glass powders one obtains mixtures from which opaquers can be manufactured which have outstanding properties and guarantee a good covering of the metal framework and good adhesion to the metal and to the facing.

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i i U IC-L-L~" LI 10. LIIV Ld" F Sl LA 0 0 4J P r- C ;3 _qC),,UL-C r7 Ch ;C 1 r 1 1 4 -propose a.si- Although the said prior art reveals that zirconium dioxide was

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4 1 '1 1 i I r rn 4 known as an opacifier for ceramic glazes, the use of larger quantities of zirconium dioxide as essentially sole opacifier addition to glass powders for the manufacture of an opaquer is neither known or suggested. It was, rather, surprising that in the case of compositions which are free om larger proportions of titanium dioxide and/or other opacifiers and contain zirconium oxide as opacifier additive to glass powders one obtains opaquers which are distinguished by outstanding properties, especially outstanding covering power and adhesion.

The present invention consists in a method for the manufacture of a priming material for the overlaying or coating of a metallic tooth crown or bridge by using a mixture and moistening the same with a liquid, wherein the mixture contains a matrix forming glass powder and as opacifier 10 to 60 ZrO 2 and, at most, TiO 2 and/or other opacifiers as hereinbefore described, the average particle size of ZrO 2 being 1 /1m 0.2 fim and the zirconium dioxide particles having a specific surface of about 1 to 20 m 2 /g.

The glass powder preferably consists essentially of the oxides of sodium, potassium, calcium, barium, boron, aluminium and/or silicon with a small proportion of 25 titanium, the TiO 2 optionally present being melted in the glass and functioning, not as an opacifier, but as a germination agent for the crystallization of leucite.

Oxides of cerium (Ce) and optionally of P and Zr may also be contained in the glass. The glass preferably contains 30 as main constituents SiO 2 Al 2 0 3 and K 2 0, preferably in respective amounts of 40 to 70 10 to 25 wt.-% and 8 to 28 Other glasses can also be used.

In a preferred embodiment, the mixture contains 20 to 45 ZrO 2 the ZrO 2 particles having a purity of i i

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i .4 '6 i" i -I iI 4 4a To manufacture the glass, the oxide mixture is melted, quenched in water and worked up in a manner known per se into a fine glass powder.

In detail, for ex-?ple, the molten oxide mixture is quenched in water and ground up in a ball mill. The glass powder is then

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Ar 4 ti S sr 1_ i c i i tempered at ca. 900 degrees C, sintering together to form a block which is quenched in water while still glowing. A granulate forms which is ground up in an alcohol/water mixture in the ball mill. The result is a slip which is dried and then passed through a screen.

This glass powder is mixed with zirconium dioxide. The mixture is manufactured in the ratio of, at most, 9 parts glass per part zirconium dioxide. Preferred mixture ratios lie between 4:1 and 1:1.5.

To manufacture the ready-to-use opaquer, the powder mixture is mixed with a liquid. For example, the powder can be admixed with C distilled water on a ceramic plate to produce an opaquer.

However, other liquids such as glycerin or glycol can also be used for the admixing process.

In a particularly preferred embodiment, 3 parts by weight glass PO are mixed with 2 parts by weight zirconium dioxide and homogenized with a further 2 parts by weight glycerin on a triple roll mill.

For application as priming material, the resultant paste is deposited on a crown with a brush and stoved at temperatures of between 800 and 1000 degrees C. The result is a covering white layer which displays no discolorations even at the metal edges, is distinguished by a high covering power and offers good adhesion between metal and ceramic. The crown is then faced with O ceramic by conventional methods.

Colour pigments can optionally be added to the powder mixture in order to endow the stoved opaquer with a tooth colour-like colour. The colouring substances can also be added during homogenization, however.

i c r i =Y-r n- i I 6 It is also possible to add other known ceramic powders to the glass powder in order to vary the coefficient of thermal expansion (CTE). The CTE value is known to be an important parameter in metal ceramic facing work and must suit the alloy which is to be faced.

Ple--S_"r i .ni m di nxi d_ partie s have an_ a erage. arti (1 i n 1 [im 0.2. The zircoi -m-d iTe particles also have a specific N= nf about I t-n 9 n T2ZI a 1 n d 2-p The following examples explain the invention.

Example 1 i- Manufacture of a melt A with high CTE: A glass of the following composition was melted in the usual way: 5.95 13.86 3.48 CaO dO 1.64 BaO 1.36 B203 16.09 A1203 0.37 Ti02 57.25 Si02.

This glass was quenched in water and ground up in a ball mill until the average granulation was ca. 80 to 100 um.

2O The glass powder was then tempered for an hour at 900 degrees C, sintering together to produce a block which was quenched in water while still glowing. The resultant granulate was ground up to an average granulat.ion of below 20 um in an alcohol/ water mixture in the ball mill. The grinding time depends on the )C size and type of the ball mill.

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7 For example 200 g coarse glass powder 800 g porcelain balls with 9 mm diameter 100 g distilled water S100 g alcohol were allowed to run on rolls for 8 hours in a 1-1 porcelain drum.

The resulting slip was dried at 100 degrees C and passed through a 60-um screen to avoid agglutinated lumps.

iO 60 g of this melt were mixed with 40 g zirconium dioxide with an average granulation of 1 um which is marketed by Magnesium Elektron under the name "Zirkonoxid This mixture was blended with 40 g glycerin to form a paste and J1} homogenized on a salve triple roll. The homogenized pas-e was Spainted onto a nickel/chromium alloy with a brush and then stoved at 960 degrees C with a 2-minute holding time. The result was a covering white matt layer of very good adhesive strength which could then be overlaid with ceramic dentin QO materials. The coating also displayed no discolorations even at the metal edges.

Samples were burned in order to check the strength and the CTE.

The following values were measured: Bending strength 143 11 N/mm 2 Flexural modulus 73000 6000 N/mm 2 CTE 100 500 degrees C 14.4 x 10-6/K SExample 2 2" 0 Using the melt A referred to in Example 1, a paste was manufactured according to the following formulation and homogenized as in Example 1: g melt A g zirconium dioxide g ceramic colour 23264 i r i i-- 8 g ceramic colour 26077 g ceramic colour 14-R-481 2 g SiO2, BET surface 200 25 (Aerosil 200 Degussa) g glycerin.

orange-yellow, based on Zr and V oxide (Degussa) yellow-brown, based on Zr, Cr, Fe, Al oxide (Degussa) dark brown, based on Si, Co, Ni, Zn, Fe, Cr, Mn oxide (Ferro) A creamy paste was obtained which could be spread well with the brush. After burning on a nickel/chromium alloy at 960 degrees C a covering, tooth-coloured layer was obtained the colour of which is the same all over.

Bending strength 161 23 N/mm 2 Flexural modulus 67000 2000 N/mm CTE 100 500 degrees C 15 x 10-6/K.

S0 Example 3 An Ivoclar ceramic powder, usual for metal ceramics, for melt configuration with a CTE 100-600 degrees C of 13.5 x 10" 6 a glass point of 585 degrees C and a dilatometer softening point of 600 degrees C was ground wet to an average grain size of um, dried and deagglomerated by screening as described in Example 1, This powder was named GM-DS.

The following mixture was manufactured: 35 g melt A from Example 1 g GM-DS 21 g zirconium dioxide 14 g ceramic colour 23264 g ceramic colour 26077 L~ ~L I .r 1 The mixture was intimately mixed in E. ball mill. It was processed by mixing 1 g of this mixture with water and depositing on a nickel/chromium alloy with a brush. The appearance was the same as in Example 2, except that a glossier Ssurface was obtained. Testing of the CTE value between 100 and 500 degrees C gave a result of 14.5 x 10-6/K, which shows that the CTE value can be varied by adding other ceramic materials.

Example 4 (comparative example with tin dioxidel Io QIn order to compare the covering power with other opacifiers, the following mixture was manufactured and processed, as described in Example 1: g melt A from Example 1 I 25 g annealed tin dioxide 17 g ceramic colour 23264 11 g ceramic colour 26077 g glycerin i S[i Processing of this mixture produced an inadequately covering I layer in which the black oxides of the nickel/chromium alloy falsified the colour. Because of the high tin dioxide content, the burning temperature of this mixture was already at 1100 degrees C, which is at the upper limit for the stoving alloys usual in dental engineering. The mixture also became discoloured when stored in the light.

I Example 5 (comparison with various opacifiers In order to compare the covering power with titanium dioxide, a special glass had to be melted and worked up as indicated in Example 1 for melt A. The melt, named melt B, had the following zomposition: F.B. RICE CO. PATENT ATTORNEYS JSi7

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10 7.12 g 11.82 g 3.2 g 1.51 g 1.25 g 14.5 g 0.34 g 59.35 g CaO BaO B203 A1203 Ti02 Si02 The following mixture was manufactured as in Example 1: g melt B g opacifier g glycerin The following table contains the opacifiers used and the test results for the processing on nickel/chromium alloys: da i rrChd i i ,i Opacifier Processing consistency Covering power Discoloration upon stoving Titanium dioxide AD Titanium dioxide R-KB-2 Titanium dioxide RN-56 Precipitated tin oxide Zirconium dioxide 1 um Zirconium silicate good good good pasty liquid pasty very good very good very good inadequate inadequate inadequate dark grey grey/brown grey/brown white white white The discolorations in the case of the samples with titanium dioxide were uneven and clearly more marked towards the metal edge, so that this discoloration was unacceptable after stoving.

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11 The samples with tin oxide, zirconium dioxide 1 um and zirconium silicate had an inadequate covering power and were likewise not acceptable.

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Claims (11)

1. A method for the manufacture of a priming material for the overlaying or coating of a metallic tooth crown or bridge by using a mixture and moistening the same with a liquid, wherein the mixture contains a matrix forming glass powder and as opacifier 10 to 60 ZrO 2 and, at most, TiO 2 and/or other opacifiers as hereinbefore described, the average particle size of ZrO 2 being 1 pm 0.2 pm and the zirconium dioxide particles having a specific surface of about 1 to 20 m2i/g.

2. The method according to claim 1, characterized in that the glass powder essentially comprises the oxides of Na, K, Ca, Ba, B, Al and Si.

3. The method according to claim 2, characterized in that the glass powder contains as main constituents: 40 to 70 SiO 2 to 25 Al 2 0 3 and 8 to 20

4. The method according to claim 1 or 2, characterized t in that the glass powder also contains oxides of Ce and optionally of P and Zr.

The method according to any one of the preceding claims, characterized in that the mixture contains 20 to ZrO 2

6. The method according to any one of the preceding claims, characterized in that the zirconium dioxide particles have a purity of 99% 30

7. The method according to any one of the preceding claims, characterized in that the mixture also contains colour pigments and/or usual additives as hereinbefore described.

8. The method according to any one of the preceding s: 35 claims, characterized in that the weight ratio of glass t V 13 powder to zirconium dioxide opacifier lies in the range from 9:1 to 1:1.5.

9. The method according to any one of the preceding claims, characterized in that the liquid is distilled water or glycerin.

The method according to claim 10 characterized in that the mixture contains 3 parts by weight glass with 2 parts by weight zirconium dioxide and 2 parts by weight glycerin in homogenized form.

11. A method for the manufacture of a priming material for the overlaying or coating of a metallic tooth crown or bridge as hereinbefore described with reference to any one of the examples. DATED this 11 day of April 1994 IVOCLAR AG Patent Attorneys for the Applicant: i F.B. RICE CO. ii i, i I I I SI 4 4^^ j vs1 'wi l 6 1 a at es a a I t a t c fi t s. ABSTRACT A method for the manufacture of a primary material for the overlaying or coating of a metallic tooth crown or bridge by using a mixture and moistening the same with a liquid is disclosed. The mixture is characterised by the inclusion of a matrix forming glass powder and as an opacifier, 10 to 60 wt.-% ZrO 2 which has an average particle size of 1pm 0. 2 hand a specific surface of about 1-20 m /g. L_ -i